Manual processing to determine the cellular/biological content of various types of biological samples, and in particular samples that contain living cells, is cost-prohibitive in many applications and is also prone to errors. Automation is also cost-prohibitive in many applications, and is inappropriate as currently practiced—using, for example, liquid handling robots—for applications such as point-of-care or doctor's office analysis.
There have been many recent advances in point-of-care diagnostic assay systems based on centrifugal microfluidic technologies. Such systems typically comprise i) a centrifugal microfluidic cartridge with reagent storage and sample processing methods, and ii) related device readers for interrogation of samples processed on such centrifugal microfluidic cartridges. However, there is an unmet need to provide a simple method of biological sample application, compared with current point-of-care centrifugal microfluidic based diagnostic assay systems, that i) is less prone to user error, ii) minimises biohazard and aerosol contamination risk, iii) removes the requirement of cartridge cleaning, iv) simplifies user workflow protocols v) simplifies cartridge manufacture and cost, and vi) integrates user fail-safe mechanisms.
Existing centrifugal-based point-of-care diagnostic assay systems typically use either i) an external transfer pipette for application of liquid samples, or ii) an inlet capillary port integrated on the cartridge, whereby the sample is applied directly onto the cartridge. While the cartridges associated with both system approaches can perform a variety of integrated sample preparation and assay tests—such as lateral flow assays, electrochemical assays, etc.—their sample application methods do not address the aforementioned unmet need.
Consider the first case of an external transfer pipette. In this instance, a biological sample is applied to the transfer pipette through capillary action upon contact by the pipette's tip with the sample. The pipette tip is then typically inserted into the centrifugal cartridge's inlet chamber which is situated close to the cartridge's centre. The sample is dispensed (or transferred), for example, through either an integrated air-displacement piston within the pipette or squeezing of a rubber bulb on top of the pipette, depending on the pipette's design. This sample application method suffers the risk of aerosol or biohazard contamination once the centrifugal cartridge is spun. While integrating an absorbent material into the cartridge's inlet chamber reduces this risk, it does not eliminate it, and further complicates the cartridge's manufacturing process. Covering the inlet chamber with a physical barrier increases cost and biohazard risk, and adds user workflow steps, thereby increasing user training requirements.
Consider the second case of an integrated inlet capillary port. In this instance, a biological sample is applied directly onto a cartridge's inlet capillary port from, for the example of whole blood, a patient's lanced finger. The inlet capillary port typically protrudes somewhat from the cartridge to facilitate both user operation and sample application. Such methods typically require advanced user training as positioning the inlet capillary port to contact the patient's finger can be problematic and lead to unsuccessful or poor quality application. Such integrated inlet capillary ports complicate the cartridge's manufacturing process adding to cost and reducing production yield. They also require the application of a physical barrier, as in the previous case, to minimise biohazard and aerosol contamination.
There are a numerous examples in the art which illustrate the first case. Examples include U.S. Pat. No. 4,898,832 (Boehringer Mannheim), JP 2008 032695 (Matsushita) U.S. Pat. No. 5,061,381 (Abaxis) and U.S. Pat. No. 6,143,248 (Gamera) which describe various sample processing methods, but all use external transfer pipettes to load the sample.
One such example of the second case in the art is US2009/205447 (Panasonic) which describes a system for transferring a sample liquid dispensed as a drop on an inlet port. The inlet port is formed to protrude in a direction away from the chamber, a recessed section is formed around the injection port, and the inlet port is arranged on the side of a rotating axis centre so that centrifugal force, upon its rotation, transfers the sample to said chamber. A hinged cover mechanism prevents biohazard and aerosol contamination.
It is therefore an object to provide a low-cost, simple sample application apparatus and method to address at least one problem known in the art.